1. Field of the Invention
Embodiments of the present invention relate to a media access control (MAC) protocol of a wireless local area network (WLAN), and more particularly, to a protocol for transmitting data through cooperation between access points (APs) in an overlapped basic service set (OBSS) environment.
2. Description of the Related Art Currently, multiple input multiple output (MIMO) communication technology for transmitting and receiving data using two or more antennas has been generalized in a wireless communication system. Further, according to standards starting from an Institute of Electrical and Electronics Engineers (IEEE) 802.11n standard, a wireless local area network (WLAN) allows two or more transmit antennas to be available. According to the IEEE 802.11n standard, up to four transmit antennas may be used. According to an IEEE 802.11ac standard, up to eight transmit antennas may be used. In addition, when using a plurality of transmit antennas, data may be transmitted using a transmit beamforming technology to improve the signal reception performance. The IEEE 802.11ac standard includes a downlink multi-user (MU) MIMO technology that enables an access point (AP) to concurrently transmit beamformed data frames to a plurality of stations (STAs).
However, according to a recent increase in the complexity of a WLAN environment, an overlapped basic service set (OBSS) frequently appears. Here, the OBSS indicates an overlapping area between a BSS corresponding to a service area covered by a single AP and a BSS covered by another AP. In an OBSS environment, the transmission efficiency may be degraded and thus, a method for performing an efficient transmission even in the OBSS environment is required.